Radar distance and altitude indicator



March 2l, 1950 M. WALLACE RADAR DISTANCE AND ALTITUDE INDICATOR 2Sheets-Sheet 1 Filed Nov. v 22, 1946 VVVIl 3MTM/bo@ MARCEL WALLACE March21, 1950 M. WALLACE RADAR DISTANCE AND ALTITUDE INDICATOR 2 Sheets-Sheet2 Filed NOV. 22, 1946 k il www@

MARCEL 'WALLACE Patented Mar. 21, 1950 INDICATOR Marcel Wallace,Fairfield County, Conn., assigner,

by mesne assignments, of one-h lf to Pano-1, ramic Radio Corporation,New Yo k, N. Y., a corporation of New York Application November 22,1946, Serial No. '111,503

23 Claims. (Cl. 343-6) This invention relates generally to telemeti'icdevices, and more particularly to devices for measuring simultaneouslythe range and the value of a measurable quantity associated with aremote device. A

It is an object of the present invention to combine measurements ofrange made -by means of pulse radar or sonar techniques withmeasurements of the value of a measurable quantity associated withtheobject ranged on.

It is a further object of the invention to make simultaneousmeasurements of range and of another quantity, range being measured interms of time required for the traverse of pulse energy from a selectedvlocation to an object and for its return, and the other quantity beingmeasured in terms of time of occurrence of the pulse in a periodic timescanning cycle.

It is still a further object of the invention to provide a system fordisplaying on the screen of a cathode ray tube indicator thesimultaneous values of pairs of measurable parameters, one of which isrange.

It is another object of the invention to provide a system for.displaying on the face of a cathode ray indicator, as unitaryindications, the ranges and altitudes of a plurality of aircraft.

It is a further object of the invention to provide a system fordisplaying simultaneously on the screen of a cathode ray indicator, thesimultaneous values of a pair of navigational parameters associated witheach of a plurality ofv aircraft.

It is still a further' object of the invention to provide a system fordisplaying at a selected location, whichvmay preferably be a groundstation, the range and altitude of each of a plurality of aircraft.

It is a morev particular object of the invention to provide a system forproviding on the :ace of `a cathode ray tube a plurality of visibleindications, in the form of linear traces each having a lengthcorresponding with range and a displacement corresponding with ameasurable quantity associated with an aircraft or other vehicle.

It is an object of the' invention in its broader aspect to provide acombined indication of the value of a measurable quantltyas transmittedfrom a distant object, and of the range of that object.

It is a further object of the inventionin its broader aspect to providea novel pulse radar system wherein the pulses are transmitted in groupsof one or more pulses each'group occurring at a time which hastelemetric significance.

It is still a further object of the invention to provide a radar systemof the pulsed type wherein the time of transmission of each pulse orgroup of pulses is controlled in accordance with the value of ameasurable quantity.

It is a further object of the invention to provide a radar system of thepulsed type wherein the time of transmission of each pulse or group ofpulsesis controlled telemetrically, and wherein the time elapsed betweentransmission and Ieception of each pulse aswell as the time oftransmission of each pulse or group of pulses are indlcated concurrentlyand as a unitary indication.

The above and still further objects and advantages of the invention willbecome apparent upon consideration of the following detailed descriptionof the invention, when taken in conjunction with the accompanyingdrawings, wherein:

Figure 1 is a functional block diagram of an airborne equipment, inaccordance with one embodiment of the invention;

Figure 2 is a functional block diagram of a groundinterrogator-responser radar, in accordance with one embodiment 'of theinvention;

Figure 3 illustrates the appearance of indications of a cathode ray tubewhen provided with control signals in accordance with the invention;

Figure 4 is a functional block diagram of an airborne transponder,arranged in accordance with a further embodiment of the invention;

Figure 5 is a functional block diagram of a groundinterrogator-responser, arranged in accordance with a further embodimentof the invention and which is adapted to oo-operate with the transponderof Figure 3; and

Figure 6 is a representation of the appearance of range-altitudepresentation on the face of a cathode ray indicator, included in theinterrogator-responser of Figure 5.

Proceeding now with a brief resume of the invention, as applied to oneparticular application thereof, there is provided aboard each of a4plurality of aircraft flying in the vicinity of a ground station, atransmitter arranged to transmit continuously signals at a frequencycorresponding with the value of a measurable quantity associated withaircraft, and which in the present application, and for purposes ofexempliiicag'on only, is taken as the altitude of the aircra Eachaircraft carries, in association with its altitude transmitter, areceiver which is also K atom tunedin accordance with the altitude oithecrai't, and which is constrained to maintainits tuning at a ilxedfrequenc'ydifference from the tuning of the transmitter. Associated withthe receiver aboard each aircraft is a pulse transmitter, which isnormally quiescent but which lis'energized inresponse to and for theduration of the reception Aoi. signals by the 4altitude tuned receiverand which when energized, transmits on a ilxed frequenc'y. which may bethe same for all the craft utilizing the system.-v A -At the groundstation is provided a receiver and a transmitter which are4 maintainedat a fixed di'erence of frequency, corresponding with the frequencydifference of tuning allocated to the airborne altitude transmitter andreceiver, and which are caused to scan synchronously over predeterminedrespective frequency spectrum portions, the ground transmitter scanningthe total band of frequencies allocated to the airborne altitudereceiver and' the ground receiver scanning the total band of frequenciesallocated to the airborne altitude transmitter.

he ground transmitter is normally maintained inoperative to transmit,but when operative transmits pulses which may be at any convenientllength and rate. The ground transmitter is rendered operative totransmit in response to reception by the ground receiver of an altitudecorresponding frequency deriving from an aircraft. Accordingly theground transmitter transmits pulses or groups of pulses, each occurringat a frequency corresponding with the altitude of ,an aircraft. Sincethe transmitter frequency is being varied in accordance with a timefunction, the pulses Fxor groups of pulses may also be considered to betransmitted at times corresponding with altitudes of aircraft.

Each airborne pulse transmitter is rendered l operative to transmit atthe same-frequency but only at such times as the airborne altitude tunedreceiver is receiving pulses from the ground transmitter. craft arereceived on a ground pulse receiver, and are caused to contribute to.the controlof a fast saw tooth wave generator, which is started vinresponse to transmission of a pulse from the ground station and stoppedin response to reception at the ground station of a pulse deriving fromthe aircraft.`

Each aircraft'receiver and pulse transmitter provides, in accordancewith-the above description, a transponder system, the receiver of whichis tuned in accordance with the altitude of the aircraft, and .which istherefore operative to transpond only at such times asthe groundtransmitter frequency, in the course of its scanning cycle, passesthrough the frequency to whichthe receiver of the transponder is tuned.

A cathode ray /indicator is provided at the ground station which iscontrolled in respect to vertical deflection in synchronism with thetun' ing of the ground transmitter. and in respect to by the fast sawtooth generator previously referred to.' Since a scanning cycle of thefast saw tooth generator is initiated in response to transmission of apulse by the ground transmitter, and since termination of the pulse,which is in turn proportipnal to range.

Since pulses are transponded from any aircraft The pulses transmittedfrom the airsynchronism with frequency scanning of the associated with.the oscillator 'l altitude corresponding frequency spectrum, thehorizontal range traces are caused to'occur at vertical positions on theface of the indicator corresponding with the altitude of the aircrafttherange of whichisbeing determined.

Proceeding now with ay more detailed description of the invention,reference is made to Figure 1 which presents in functional block diagraman aircraftinstallation, in accordance with the present invention. l

'A continuous, wave oscillator l is controlled in respect to frequencyin correspondence with a associated with a tuner v3, .which may take theform of a condenser, an inductance, or a combination of the two, andwhich is so as to determine its tuning.

While the range of frequencies utilized bythe oscillator l is a matterof choice, in view of various considerations of a practical nature Ihave selected a virtue of residuary coupling between antennas l and l.

The mixer 6 feeds into an I. F. amplifier 3,

tuned to a center frequency of 5 mc., for a reason nafter to applied toenergize a pulsed oscillator l0, which radiates energy at a fixedfrequency F, over an antenna il.

The mixer 6, I. F. amplifier 8, and detector 9 are designed and intendedfor the reception of pulse being caused to pulse drawings, amplifier 2|,which in turn feeds a power amplifier 22 having an associatedtransmitting antenna 23. The power amplifier is normally inactive, beingprovided with pulsed energy by a pulser 24, and being operative totransmit .pulses when,`and only when; the pulser 24 is energized. Theoscillator 20, buffer amplifier 2|. and power amplifier 22 are gangtuned by condensers 25 associated therewith, the condensers 25 beingrotated mechanically by means of a motor 26, the drive between the motor26 and the condensers 25 being indicated conventionally by dotted line21. The frequency range of the oscillator in the course of the frequencyscanning action consequent upon rotation of the condensers extends from153-158 mc., to match the band of frequencies translatable by the mixer6, the 5 mc. I. F. amplifier 8 and detector 9, when operated inconjunction with the local oscillator I, having a range of 148-153 mc.

The oscillator 20 is utilized not only as a, control oscillator todetermine transmitted ground frequencies, but also as a local oscillatorfor a ground receiver section, operating on the superheterodyneprinciple, and comprising a mixer 28 and an R. F. amplifier 29, thelatter deriving signals from a receiving antenna 30. The amplier 29 andthe mixer 28 are gang tuned respectively by condensers 3 I, which arecontinuously rotated, by mechanical coupling 21, in synchronism with thecondensers 25, and which effect scanning of the tuning of the receiversection over a range of frequencies extending from 148 to 153 mc.,corresponding with the range of frequencies transmittable by oscillatorI as a measure of altitude. By virtue of the synchronization of therotations of condensers 3| and 25, the receiver tuning and thetransmitter output frequency maintain a fixed frequency difference of 5mc.

The output of the mixer 28 is applied to an I. F. amplifier 32, tuned toa center frequency of 5 mc.,

. the output of the amplifier 32 being detected in a detector 33.

The output of the detector 33 is applied over a lead 34 to the pulser24, and causes energize.- tion thereof, so that detection of signals bydetector 33 is accompanied by transmission of one or more pulses by thepower amplifier 25 at a time and at a frequency corresponding with thetime of energization of puiser 24.

The motor 26 actuates not only the condensers 25 and 3|, but alsocontrols a sawtooth generator 35 to produce a sawtooth voltagesynchronized with the tuning action of the condensers. The output of thesawtooth generator 35 is applied to the vertical plates 36 of a cathoderay oscilloscope 31, to cause vertical scanning of the beam of theoscilloscope in synchronism with the tuning of the receiver andtransmitter sections of the ground equipment.

The beam of the oscilloscope 31 is normally biased beyond or to cut-ofi,by a control grid 38, which is connected to the detector 33 in suchfashion that intensifying voltage is applied to the grid 38 upondetection of signals by detector 33.

Reviewing the operation of the apparatus described, let us assume thatthe oscillator I aboard an aircraft is tuned to a frequency f, fallingin the range 148-153 mc., and specifically 150 mc. corresponding with analtitude of 4000 ft. As the ground receiver scans the range 148-153 mc.,it periodically passes through the frequency f=150 mc., the oscillator20 being at that instant tuned to a frequency f-1-5 mc.=155 mc. Theoutput of R. F. amplifier 29 at 150 mc. and of oscillator 20 at 155 mc.are mixed in mixer 28 and provide a 5 mc. output, which is amplified anddetected to provide an intensifying signal for the grid 38, and hence acathode ray beam of sufiicient intensity to produce a clearly visibleindication at a vertical level on the face of the indicator 31corresponding with an altitude of 4000 ft. The output of detector 33 isalso applied to energize puiser 24, which causes transmission by thepower amplifier 22 of one or more pulses at a ground transmitterfrequency corresponding also with an altitude of 4000 ft., to wit, 155mc.

The output of the amplifier 22 may be effectively received only aboardan aircraft which is at an altitude of 4000 ft. since only such anaircraft has an oscillator I tuned to a frequency of mc., and is thuscapable of converting a received signal at mc. to an I. F. frequency of5 mc.

The aircraft at 4000 ft. translates pulses deriving from the poweramplifier 22 into pulses at the output of detector 9, which are appliedto the oscillator I0 to cause transmission of a pulse at frequency F foreach received pulse at frequency f+5 mc.

The pulse output of the oscillator I 0 is received at the ground stationby a pulse receiver 40, which feeds a detector 4|, the output of whichconstitutes a cut-off pulse for the sawtooth generator 42. The latter issupplied with start pulses by an amplifier 43, connected over lead 44with the puiser 24. Transmission of a pulse by power amplifier 22 isaccordingly accompanied by initiation of generation of a sawtoothvoltage in the generator 42, and reception at pulse receiver 40 of apulse transmitted from the transponder oscillator I0 in response to theground originating pulse results in termination of the voltage build upof the sawtooth generator 42 and its reconditioning for a further cycleof operation. The output of the generator 42 is applied to thehorizontal plates 45 of the indicator 31, so that horizontal traces areproduced thereon, at such times as the cathode ray beam is intensified,which have a length proportional to the range of a transpondingaircraft. Accordingly, a linear indication 46 will be provided (seeFigure 3) at the indicator 31, in response to signals from each aircraftin the vicinity of the ground station, the indications having a lengthcorresponding with the range of the craft, and a vertical displacementcorresponding with the altitude of the aircraft.

Normally the character of the indications 46 will depend on thecharacter of the puiser 24. Should the puiser transmit asingle puise inresponse to each signal derived from detector 33 the indications 46 willcomprise a single line. Should the puiser 24 be constrained to produce agroup of pulses in response to each signal from detector 33, successivepulses of the group will occur at slightly different altitudes, sincethe various circuits of the equipment are of finite bandwidth, andconsequently respond over a slight but appreciable range of valuescentering about the nominal values referred to in the above descriptionas the frequency of the ground equipment varies in the course of ascanning operation.

Still a further embodiment of the present invention is illustrated in'Figures 4 to 6 inclusive of the drawings.

Referring now more specifically to Figure 4 of the drawings there visillustrated a transponder system |00, which is indicated to be airbornefor the purpose of the present invention and which may be located in anaircraft or an airborne missile. The transponder |00 comprises asuperheterodyne type receiver IOI, having associated therewith areceiving antenna |02, and is adapted to receive and detect pulses ofthe character generally transmitted by pulse type radar equipments andinterrogator-responser equipments.

The output of the receiver, in the form of detected pulses, is appliedto a transmitter having an antenna |04 associated therewith as aradiating element, and the transmitter |03 is arranged to transmitsignals only in response to the appplication to said transmitter of adetected pulse from the receiver |0I.

The tuning of the receiver |0| and of the trans.- mitter |03 iscontrolled by -an oscillator |05, which acts simultaneously as the localoscillator of the receiver |0| and as the master oscillator 'for thetransmitter |03. By virtue of this expedient the transmitter |03 and thereceiver |0| are caused to track in respect to frequency, maintaining aconstant difference frequency therebetween, equal in value to theintermediate frequency of the superheterodyne receiver 0|.

The oscillator |05 may be controlled in respect to frequency in any oneof a number of ways, and in response to any one of a number of differentphysical quantities. I have chosen to exemplify the present invention asapplied to the measurement of atmospheric pressure and consequently oflocal altitude, but the invention is not limited to this application,and may in fact be utilized in conjunction with any type cf measuringdevice which is capable of determining and controlling the frequency ofan oscillator, and it is believed that there are substantially nomeasuring devices which are not so.capable, by means of adaptationswhich are per se known to those skilled in the art.

In one actual embodiment of the invention the receiver |0| was providedwith an I. F. amplifier having a centerY frequency of 5 inc. and alrela-,tively narrow pass band. The receiver |0| was then made tunable overthe range of frequencies 153-158 rnc.V by arranging the altitudecontrolled oscillator |05 to have a range of frequencies extending from148-153 mc., over the range of altitudes which it was desired to.ymeasure. The transmitter |03, then, being controlled in respect tofrequency directly by the oscillator |05 is caused to transmit signalsover the band of frequencies 148-153 mc., and is .maintained at alltimes at a frequency 5 mc. below that of-the -receiver |0|.

A ground equipment adapted for cci-action with the transponder .|00 isillustratedin block diagram in Figure 5 of the drawings, and constitutesin essence a frequency scanning interrogatorresp'onser, the interrcgatorcontinuously scanning the band of frequencies allocated to the airbornereceiver 0| and the responser continuously scanning the band offrequencies allocated to the airborne transmitter |03. By virtue of thisarrangement the transponder |00 is operated only at one point in thescanning cycle of the interrogator responser, and indicator means areprovided for indicating in coordinated fashion the 8 plished by means ofa condenser 20|, connected intuningrelation to the oscillator 200 anddriven by a motor 202 at any convenient rate, periodically to scan overits assigned range.

The oscillator 200 controls the frequency of oscillation of a poweramplifier 203, the input of which is connected to the output of theoscillator 200, and which is periodically tuned similarly to theoscillator V200 .by means of a condenser 204 ganged with the condenser20|. An antenna 205 is' connected to the output of the power amplifier203, and is designed efficiently to radiate the output thereof.

-The power amplier 203 is pulsed by a puiser 200 in accordance 'withknown radar practice at a rate such that at least one pulse istransmitted for every small increment in frequency during the scanningcycle. The action of the pulser 208 serves, in response to each pulse,to initiate generation of a fast range-indicating sweep voltage. in thegenerator 201, the output of the latter being applied to the horizontalplates 208 of an oscilloscope 209. The beam of oscilloscope 209 isnormally biased back beyond or to cut-olf, and is subject to intensitycontro1 in response to voltage applied to its intensity control grid 2I0.

A sweep generator 2|| is provided which produces a slow saw-tooth sweepvdltage which is synchronized with the scanning action of the condensers20| and 204, the sweep voltage being applied to the vertical plates 2| 2of the oscilloscope 209. The law of variation of the vertical sweepvoltage is so correlated and synchronized with the frequency variationor scanning action of the oscillator 200 that theinstantaneous verticalcoordinate of the beam of the oscilloscope 200 is ameasureatrall times,of the instantaneous oscillator, and consequently of Vtransmission ofthe interrogator' the frequency of sectionl of the apparatus of Figure5.

' sweep generator 201 -is caused to produce a horiinstant in thescanning cycle at which transponse takes place, as well as the range ofthe transponding equipment. Since the instant at which transponse takesplace is a function of the frequency of the transponder which in turn isa function of the magnitude of a measured quantity, it will be apparentthat the indications provided at the interrogator-responser constitute asimultaneous measurement of the range of a transponder and of the valueof a measurable quantity associated with the transponder.

Referring now more 'specifically to Figure 5 of the drawings, anoscillator 200 is provided, which is turnable over the `range 153-158mc., inclusive, in the present embodiment of the invention, tocorrespond with the selected tuning range of the receiver |0I. Tuning isaccom- 15 2l. the

zontal deflection of the cathode ray beam of the oscilloscope 209 inresponse toleach transmitted pulse, in a manner well known per se in theradar art, the entire face of the oscilloscope is scanned 1 by thecathode ray beam once for each scanning cycle of the sweep generator.

Pulses transmitted by the power amplifier 205 are transmitted over theantenna v205, which may be directional if desired, and upon reception bythe transponder |00 at such times as the pulse carrier frequency fallswithin the transduction range of the transponder |00, are repeated atthe frequency of the transmitter |03 and received and detected by theresponser section of the apparatus illustrated in Figure 5 of thedrawings. 'I'he responser section comprises a receiving antenna 2I3,which may be directional, if desired, and which applies signalsintercepted thereby to an RfF. amplifier 2M. The output of the R. F.amplifier 2M as well as signal derived from the oscillator 200 areapplied to a mixer 2| 5, which in turn feeds an I. F. amplifier 2|6,tuned to a center frequency jof 5 mc., to correspond with the differencefrequency between transmission and reception allocated to the presentlydescribed embodiment of the invention. The output of the mixer 2|5 isdetected in a detector 2H 2|0, to cause intensification of the beam ofthe oscilloscope 209. Y

The R. F. amplier 2M and the mixer 2|5 are tunable by means of gangedcondensers 2H and latter being actuated in a continuous Since, as hasbeenstated heretofore, the fast'v and applied over lead 2|8 to theintensity grid and periodic frequency scanning cycle by the motor 202,in synchronism with the scanning action of the condensers 20| and 20|.The actual timing of the R. F.amp1ifier 2li and of the mixer 2|5 takesplace over a range of frequencies 148-153 mc., corresponding with therange of possible transmission frequencies of the transmitter |03, andthe instantaneous` frequency of tuning of the R. F. amplifier 2 Il andof the mixer 2|5 is maintained continuously at a value 5 mc. below thatof the oscillator 200 and the power amplifier 203. By virtue of theabove arrangement the responser section of the interrogator responser ofFigure 5 is enabled to receive signals at any given instant of time onlyfrom transponders which are at a proper altitude to be interrogated bythe interrogator section of the apparatus of Figure 5, at thatparticular instant of time. The pulse output of the detector 2H, beingapplied to the intensity control grid 2|0, causes production of a brightspot on the face of the oscilloscope 209 at a point corresponding withthe range of the interrogated transponder, in terms of its horizontalco-ordinate, and that point has simultaneously a vertical co-ordinatecorresponding with the altitude of the interrogated transponder, byvirtue of the correlation existing between the vertical position of thecathode ray beam and the frequency scanning action of the lnterrogatorresponser. Since transponders at different altitudes are interrogated insuccession, :und since the time of pulse returns from each transponderwill be determined, still further, by

the range of that transponder, the simultaneous positions of a pluralityof aircraft, in respect to both range and altitude may be presented, bythe action of the present invention, as bright spots on the face of theoscilloscope 209, each spot having a. vertical coordinate corresponding-with the altitude and a horizontal coordinate corresponding withtherange vof one aircraft, as i1- lustrated in Figure 6 of the drawings.

It will, of course, be clear, since the controlled oscillator of thetransponder may be controlled in accordance with any desired physicalquantity, that the presentation of Figure 6 may be caused to represent aplot of the values of any selected physical quantities associated with aplurality of transponders |00, against the ranges of those transponders.By way of example, the controlled oscillator may be made responsive tobearing or speed of an aircraft or rocket,-

temperature or degree of atmosphereric ionization adjacent to anaircraft or rocket, rate of climb or descent of an airborne missile, aswell as many other quantities too numerous to mention. Nor is theapplications of the invention limited to use aboard airborne devices,since bearing, speed, etc., of vehicles or other devices adjacent to theearth may be likewise measured remotely, by the use of my invention,

It will further be obvious, while I have disclosed my invention asapplied to radar equipments, and as utilizing pulses of electromagneticenergy, that similar results may be obtained in application to sonarequipments, utilizing pulses of sonic or supersonic energy, whereby aeld of application to submarine telemetrics is opened up.

While I have described my invention, together with various applicationsthereof, in terms of certain specific embodiments thereof, it will beclear that vari-ations of the specic arrangements disclosed may beresorted to without departing from the true spirit of the invention,which is denned particularly in the appended claims.

- l0 What I claim and desire to secure by Lette Patent of the UnitedStates is: A

1. In combination, means for measuring range of a remote elevated objectfrom a predetermined location'- by measuring transmission time ofradiant energy between said predetermined location and said remoteobject, means for providing a displaceable indication of said range,means at said remote elevated object for characterizing said radiantenergy in accordance with the elevation of said elevated object, andmeans responsive to said radiant energy so characterized for displacingsaid indication of said range in accordance with said elevation.

2. In combination, a normally quiescent transmitter, means for varyingthe tuning of said transmitter periodically over a predetermined rangeof frequencies, remote means for transmitting signals having a frequencywhich bears a predetermined relation to the value of a measurablequantity, and means responsive to said signals for establishingtransmissions from said transmitter only at times in the course of saidperiodic tuning corresponding with the value of said measurablequantity,

3. In combination, a rst transmitter for transmitting signals having atleast one characteristic which is dependent for its value on the valueof a measurable quantity, a second transmitter adapted to transmitpulses, means normally maintaining said second transmitter quiescent,means for cyclically tuning said second transmitter over a predeterminedfrequency spectrum, means responsive to said signals for disabling saidmeans for normally maintaining said second transmitter quiescent at apoint in the tuning cycle of said second transmitter which bears apredetermined relation to a value of said at least one characteristic.

4. In combination, a first transmitter tunable to transmit signals at afrequency within a selected band of frequencies which is determinedinaccordance with its altitude, a normally quiescent pulse transmitter,means for periodically varying the tuning of said pulse transmitter overa predetermined band of frequencies, means for energizing said pulsetransmitter to transmit pulses at points in the periodic Variable tuningthereof which are determined by the frequency of said signalstransmitted by said first tr-ansmitter, and a pulse repeater associatedwith said first transmitter and responsive to pulses deriving from saidnormally quiescent pulse transmitter to repeat said pulses.

5. The combination in accordance with claim 4 wherein is furtherprovided in association with said pulsel transmitter an indicatorelement deectable in two dimensions. means for deflecting said elementin one of said two dimensions in synchronism with said tuning of saidpulse transmitter, means responsive to each transmitted pulsetransmitted by said pulse transmitter for initiating a deection of saidelement in a second of said two dimensions, means for receiving pulsesfrom said pulse repeater, and means responsive to pulses received bysaid last named means for modulating said initiated deections.

6. A distance measuring equipment comprising, a tunable transmitter fortransmitting pulse energy to remote objects, a tunable pulse receiverfor receiving pulses transmitted by said .translmitter upon return ofsaid pulses from said remote objects, means for synchronously andcyclically tuni'ng said transmitter and said receiver,

. 11 and means for maintaining a fixed frequency difference between thefrequency of said receiver and the frequency of said transmitter duringsaid tuning. f

'7. A distance measuring equipment comprising, a control receiver,apulse transmitter, a pulse receiver for receiving pulses repeated from aremote object in responseto pulses transmitted by said pulsetransmitter, and means responsive to signals received by said controlreceiver for determining times of transmission of pulses transmitted bysaid pulse transmitter.

8. The combination in accordance with claim 'I wherein said pulsetransmitter is cyclicallytunable over a predetermined band offrequencies.

9. The combination in accordance with claim 7 and further comprisingmeans for cyclically tuning said pulse transmitter and said controlreceiver in synchronism. said pulse receiver being fixed tuned.

10. In combination, a first transmitter carried aboard an aircraft,means for tuning said first transmitter in accordance with the altitudeof said aircraft, a puise repeater carried aboard said aircraft having areceiver tuned in accordance with the altitude of said aircraft, aground located pulse transmitter, a ground located pulse receiver havingmeans for cyclically tuning said receiver to receive signals from saidfirst transmitter at one point only in the tuning cycle of said pulsereceiver, means for cyclically tuning said ground located pulsetransmitter to transmit pulse signals periodically within the tuningrange of said receiver carried aboard said aircraft, means maintainingsaid ground located transmitter normally inoperative to transmit, andmeans responsive to reception of a signal by said ground locatedreceiver for causing transmission ofy pulses by said ground locatedtransmitter.

11. The combination in accordance with the claim 10, and furthercomprising an indicator having means for providing an indicationdefiectable in two dimensions, means for defiecting said indication inone of said dimensions in synchronism with said cyclical tuning, andmeans for producing a deflection of said indication in the other of saiddimensionsvthe length of which is a function of the time elapsed betweentransmission of a pulse by said ground located transmitter, and returnof said pulse to said ground located transmitter via said pulse repeatercarried aboard said aircraft.

12. The method comprising the steps of transmitting pulses from a firstlocation, repeating said pulses from a remote object, receiving saidrepeated pulses at said first location after repetition from said remoteobject, controlling the times of transmission, relative to referencetimes, of each of said pulses from said rst location in accordance withthe value of a measurable qua-n- .'tity, and displaying as a unitaryindication time lapses between said times of transmission of each pulsefrom said first location and said reference times and the time elapsedbetween transmission and reception of said pulses.

13. The method comprising the steps of transmitting periodic pulses,repeating said pulses from a remote object, receiving said pulses afterrepetition from said remote object, controlling the periodic times, withrespect to a reference time, of transmission of said pulses, inaccordance l with the value of a quantity as measured at said remoteobject, and providing simultaneous indications of said times oftransmission with respect to said reference time and of the elapsed ,l12 time between .transmission and reception of said pulses.

i4. The method in accordance with claim 13 whereinsaid measured quantitycorresponds with a navigational parameter associated with'saiciy remoteobject. l

15. The method in accordance with claim 13 wherein said measuredquantity corresponds with the altitude of said remote object. l

lfIn combination, a transmitter for transmitting signals to a remoteobject for return therefrom, a receiver for receiving said signals afterreturn from said remote object, an indicator Ifor providing a visualdisplay of the range of said remote object as derived from said signals,means at said remote object for characterizing said signals inaccordance with the value of a measurable quantity, and means formodifying said visual display in response to said signals, to rendersaid visual display indicative of said value of said measurablequantity.

17. In combination, a pulse transmitter for transmitting pulses ofradiant energy, means for predetermining the'frequency of said radiantenergy, means for periodically sweeping said predetermined frequencycontinuously between upper and lower limits of a predetermined range offrequencies in accordance with a predetermined law of variation offrequency with time, a remote pulse receiver, a remote pulse transmittercoupled with said remote receiver to transmit pulses only in response toreception of pulses by said pulse receiver, means for tuning said remotepulse receiver to a predetermined frequency within said predeterminedrange of frequencies to establish pulse transmission from said remotepulse transmitter only at times determined by said predetermined law ofvariation of frequency with time and said last mentioned predeterminedfrequency. 4

18. In combination, an indicator having means for providing anindication capable of motion in a Iplurality of direction, a deviceremote from said indicator comprising means for measuring the value of ameasurable quantity, means coupled with said indicator for measuring theraHnge of said device, said last named means comprising means fortransmitting signals to said device and for receiving responded signalsfrom said device, means at said device for imposing on said respondedsignals an information bearing characteristic determined in accordancewith said value of a, measurable quantity, means for determining saidindication in one of said plurality of directions in accordance withsaid rangeyas determined by said means for measuring range, and meansfor determining the indication of said indicator in another of saidplurality of directions in accordance with said value of a measurablequantity as determined by said means for measuring. p

19. In combination, a pulse/repeater comprising a receiver for receivingpulses and a transmitter for repeating received pulses, and meansresponsive to the value of a measurable quantity as measured adjacentsaid pulse repeater for determining the tuning of said transmitter andof said receiver.

20. In combination, an indicator having means for providing anindication element capable of motion in two dimensions, means remotefrom said indicator for measuring the value of a quantity, means coupledwith said indicator for measuring range from a predetermined point ofsaid rembte means by measuring transmission time of wave energy betweensaid remote means and said predetermined point, means for indicatingsaid range on said indicator in terms of motion of said indication inone of said dimensions, and means responsive to said means remote fromsaid indicator for displacing said indication in the other oi' saiddimensions in accordance with the value of said quantity.

21. In combination, a continuously transmitting elevated transmitter ofwave energy, means for determining the frequency-of said wave energy inaccordance with the altitude of said transmitter, a remote receiver forsaid wave energy, means for tun-ing said receiver periodically throughthe frequency of said wave energy,

,Y whereby said receiver receives wave energy from said transmitterperiodically at times, measured from a reference time,tdetermined bysaid altitude of said transmitter, and means responsive to reception ofsaid wave energy by said receiver for transmitting a pulse of furtherwave energy.

22. In combination, a continuously transmitting elevated transmitter ofwave energy, means for determining the frequency of said wave energy inaccordance with the altitude of said transmitter, a remote receiver forsaid wave energy, means for tuning said receiver periodically throughthe frequency of said wave energy, whereby said receiver receives waveenergy from said transmitter periodically at times, measured withrespect to a reference time, determined by said altitude of saidtransmitter, means responsive to reception of said wave energy by saidreceiver for transmitting a pulse of further wave energy, means locatedproximately to said elevated transmitter for receiving said pulse offurther Wave energy and for re-transmitting a responsive pulse of waveenergy, and means located proximately to said remote receiver forreceiving said responsive pulse o! wave energy and `for translating saidresponsive pulse into an inaccordance with elevation of said aircraft.

MARCEL WALLACE.

REFERENCES CIT ED The following references are of record in the le ofthis patent:

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